Microwave Absorbing Property Of BT-NZFO Composite Material

Microwave absorbing materials play important role both in military and civil area.Though the traditional single phase materials possess certain microwave absorbing property,it can not meet the higher need of application with microwave absorbing material.Scientists over many countries are looking forward to better kind of microwave absorbing material.Ferroelectric/ferromagnetic composite material is a kind of material which shows dielectric property and magnetic property at the same time.Thus it may bring better microwave absorbing property than single phase material.However the effect of compound law makes the property of the composite lower than single phase.The introduction of percolation theory can solve this problem and make the composite material possess both fine dielectric property and magnetic property.The problem of finding new material with better microwave property is thus solved.Ferroelectric/ferromagnetic composite material with good microwave absorbing property is then obtained.BT/NZFO(BaTiO₃/Ni_0.5Zn_0.5Fe₂O₄) composite powders and ceramics of different constitution were prepared by sol-gel method successfully.The constructure and formation were analyzed by XRD and SEM separately.The dielectric and magnetic properties as well as microwave absorbing properties were investigated by Angilent E8363B PNA Network Analyzer.The result shows that BT/NZFO composite powders and ceramics possess good microwave absorbing property.The largest RL of the composite powders and ceramics are -64.2dB and -73dB seperately,which are 20-100%higher than the values normally reported(-20dB to -30dB).Largest bandwidth of the composite powders and ceramics reaches 6.2GHz and 6.1GHz seperately,about 1-2 times of the values normally reported(1-3GHz).With the increasing NZFO content in the BT-NZFO composite powder,the change of RL values of the composite powder heat treated at different temperatures show different discipline.The RL values of the composite powder heat treated at 550℃decreases first and then increases while the RL values of the composite powder heat treated at 750℃and 850℃increases first and then decreases.This is closely related with the structure and structure of the composite powder.The microwave absorbing property of the composite powders become higher as heat treatment temperature increases.When the heat treatment temperature increases from 550℃to 850℃,the RL value of the composite powder with NZFO content of 0.7 increases from -20.4dB to -58dB,and the bandwidth of it increases from 2.SGHz to 4.2GHz.The microwave absorbing property of the composite ceramics increases with the increasing sintering temperature.When sintering temperature increases from 1150℃to 1270℃,the RL value of the composite ceramics increases from -39.6dB to -73dB,and the bandwidth increases from 3.1GHz to 4GHz.While the NZFO content in the composite system increases, the frequency at which the RL value reaches the largest moves toward higher frequency.Thus the frequency at which RL peak appears can be controlled via18GHz-40GHz by setting the NZFO content.Most of the attenuation constant of the BT-NZFO composite are higher than 400GdB,which is 1 times higher than the reported values:pure BT(203GdB) and 10 times higher than pure NZFO(43GdB).